The purpose of this project is to obtain a pseudo-three-dimensional distribution of extravascular lung water and explore the following: a) To develop more sensitive and accurate technique for measurement of lung water. b) To study the regional distribution of edema induced by raising pulmonary venous pressure, fluid overload, or by infusion of toxic substances, i.e. endotoxin, bromocarbomine. c) To investigate the labeling of intravascular and total lung water pools by inhalation of C15O and C15O2 radioactive gases. RB.